Slip compensated manipulation with cooperating multiple robots

Cooperating multiple robots may experience slips between their end-effecters and the object when they make no rigid grasps, as is the case of manipulating fingers. Consequently, these slips make the system unsuccessful to execute a job properly and can even cause a failure of control. Slip can be avoided by defining multiple constraints of grasping forces and usable workspace, but these constraints limit the utilization of a robotic system. The researches on finger grasps have been assuming no slip but, in contrast, this paper takes it as the main topic. The slip phenomenon is analyzed and generalized for a planar multiple robot system, manipulating a geometrically regular-shaped object. Different slip configurations are introduced and methods for their detection are proposed. This detection considers no sensors for the object's posture rather utilizes only the finger-tip position informations. Consequently, it is possible to realize exact manipulation of an object and stability of control with minimal sensors.